1. Field of the Invention
The present invention relates to a control apparatus and a refrigerating apparatus.
2. Description of the Related Art
A compressor provided in a refrigerating apparatus may lock due to some abnormalities such as overheating and a slow leak of a refrigerant. When the compressor locks an overcurrent flows, and if such a situation is left as it is, then a coil of the compressor motor burns out, leading to destruction of the compressor. Thus, a common refrigerating apparatus includes a protection circuit (e.g., overload relay of bimetal, etc.) to protect the compressor against overcurrent or overheating. It is desirable that the abnormality causing locking of the compressor is resolved within a Short time, but if the abnormality continues for a long time, the protection circuit is turned on and off repeatedly, possibly resulting in welding of the bimetal in the worst case.
On the other hand, in a so-called ultracold freezer configured to contain biotic samples and cool an inside of the freezer to a temperature lower than or equal to −80° C., if cooling capacity is lost due to problems such as locking of the compressor, precious biotic samples contained therein is damaged. Thus, there is one that is doubly provided with freezing circuits to prevent such an damage, so that even if one freezing circuit (e.g., compressor) fails, the other remaining freezing circuit will secure the cooling capacity, thereby avoiding the frozen samples from being thawed (Japanese Laid-Open Patent Publications Nos. 2006-68122 and 2010-65925).
If the locking of the compressor results in the welding of the bimetal, an overcurrent continues to flow, and therefore a circuit breaker (so-called breaker) that protects a system as a whole is operated. In the apparatus doubly provided with freezing circuits described above, in order to prevent the whole system from getting down due to the locking of the compressor in the one freezing circuit, an individual circuit breaker is further provided, in series with the overload relay, for each of the two freezing circuits. Such an individual circuit breaker is realized by employing a manual-reset-type circuit breaker so as to prevent re-welding, as well as by being set such that the circuit breaker is operated before a main circuit breaker, which protects the whole system, is operated.
Incidentally, when a power supply voltage fluctuates, a voltage drop may cause the compressor to lock. An overcurrent flows in this case as well, however, if the individual circuit breaker of the manual-reset-type is operated at this moment, the freezing circuit remains at rest even after voltage recovery unless a user resets the circuit breaker, which prevents the initial freezing capacity from being used.